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Autos au naturale

The biodegradable resin polylactic acid (PLA) is making its mark in fiber, film, spunbond, and sheet applications. To date, however, use in injection-molded products has been restricted because of the material''s slow crystalization rates, which result in poor heat resistance and extended molding cycle times. However, Japanese firm Unitika Ltd. (Osaka, Japan) says it has overcome this issue by developing a PLA/clay nanocomposite that employs silicate platelet fillers in a loading of several percent. As a result, the material is migrating into more applications, particularly in the automotive market.

Terramac injection grades exhibit thermal and mechanical properties that are claimed by Unitika to be nearly equal or superior to PS, ABS, and PP. Moreover, Unitika has made refinements to the PLA resin itself that render it resistant to hydrolysis for up to 10 years. Conventional PLA readily degrades through hydrolysis at elevated temperatures (more than 60C) under high humidity.

Unitika is targeting personal computer, electronic device, office automation equipment, and automobile interior-component applications for Terramac. It plans to sell 3000 tonnes of the injection grades in 2005. The grades currently sell for ¥600-800/kg, but this could come down once production capacity increases at Cargill-Dow (Minnetonka, MN), which supplies the base resin to Unitika, are completed. Unitika is targeting overall sales of Terramac—including film (biaxially oriented and blown), sheet for thermoforming, fiber, spunbond, and resin for injection and blowmolding—at 10,000 tonnes as soon as possible.

One Japanese automaker employing biodegradable parts is Toyota Motor Corp. (Aichi, Japan). The Raum hatchback, introduced in May 2003, features a spare-tire cover comprised of PLA fibers compounded with kenaf (East Indian hibiscus) fibers.

Stephen Moore

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